Continued construction of a physical and genetic map of the & mutants chromosome will lay the foundation for further genetic analysis of & mutants and other streptococci. To this purpose completion f the ApaI and SmaI maps aligned with the NotI map and addition of new genes that have been sequenced and/or cloned from & mutants and related bacteria will continue. For comparative purposes and chromosome structure/function analysis we will construct physical maps of other oral streptococci and compare them to & mutants. During the next five years a study of the regulation of & mutants genes controlled by sucrose and by catabolite repression will be initiated using newly developed Gram-positive gene fusion reporter system. The identification of sucrose-controlled genes will involve the use of gene bank S. mutants DNA in an integrative promoter-probe plasmid that uses LacZ as reporter gene. e study of catabolite repression will require the development of a double reporter system using LacZ and gusA; this system will be of general utility for studies of S. Mutants.